<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<style>
    .aa{
        overflow: hidden;
        width: 50px;
        height: 50px;
        background-color: #00ee00;
    }
    .bb{
        position: relative;
        width: 100px;
        height: 100px;
        background-color: #0000ff;
    }

</style>
<body>
<div class="aa">
    <div class="bb"></div>
</div>

<div class="aa" style="position: relative">
    <div class="bb"></div>
</div>


</body>
</html>